122 U.S. NATIONAL MUSEUM BULLETIN 275 



pyramidum pyramidum Geoffroy, as known from Giza Province, 

 Egypt. The nominate subspecies is significantly larger, however, in 

 all external and cranial measurements, particularly in the breadth of 

 the zygomatic arches and the length of the nasals. The two subspecies 

 are separable primarily by differences in color, the nominate subspecies 

 being noticeably darker in dorsal color with greater suffusion of dark- 

 colored hairs. Typical G. p. pyramidum also have darker and more 

 conspicuously bicolored tails, darker pencils, darker ears, darker and 

 less conspicuous postauricular and supraorbital patches, and darker 

 color around the entire circumorbital area (in many specimens of G. p. 

 tarabuli, the suborbital and postauricular patches are almost pure 

 white) . 



From two specimens (BM, nos. 13.8.6.53 and 13.8.6.60) representing 

 Gerbillus pyramidum hirtipes from Ain Sefra, southwestern Algeria, 

 G. p. tarabuli is paler and less brilliant in dorsal color, has a longer tail 

 with a more pronounced pencil, and is markedly larger in all other 

 external and cranial measurements. 



For comparison with Gerbillus pyramidum hamadensis, see account 

 of that subspecies. 



Remarks. In the original description, Thomas (1902) used the 

 darker color of G. p. pyramidum to separate these two subspecies, but 

 stated that, in the size and proportion of the skull, the two forms were 

 somewhat comparable. Setzer (1957) stated that gerbils representing 

 G. p. tarabuli were somewhat smaller but darker in color than those 

 representing G. p. pyramidum from the Nile Valley of Egypt. These 

 findings are in partial disagreement with mine, probably because the 

 above comparisons were based on smaller series, as these workers had 

 fewer specimens available at the time. Also Setzer included specimens 

 from Socna and Bir Fergian, Tripolitania Province, within G. p. 

 tarabuli. Gerbils from these localities are now known to represent a 

 subspecies distinct from G. p. tarabuli and significantly darker in 

 color. 



Ellerman and Morrison-Scott (1951) placed Gerbillus jloweri Thomas 

 in synonymy under G. p. tarabuli and thus extended the range of 

 G. p. tarabuli to include portions of eastern Egypt and Sinai. Subse- 

 quently, Setzer (1958) questioned such a wide distribution for a 

 subspecies and designated Gerbillus pyramidum jloweri as a separate 

 subspecies based on its lighter color, more inflated auditory bullae, 

 smaller molariform teeth, more laterally curved anterior palatine 

 foramina, and less open pterygoid fossae. It is now known that G. p. 

 tarabuli is not part of the mammalian fauna of Egypt but is limited 

 in its distribution to the Libyan Fezzan; in all probability it occurs in 



